Package org.apache.cassandra.index.sasi.utils

Class RangeUnionIterator<K extends java.lang.Comparable<K>,​D extends CombinedValue<K>>

  • Type Parameters:
    K - The type used to sort ranges.
    D - The container type which is going to be returned by Iterator.next().
    All Implemented Interfaces:
    com.google.common.collect.PeekingIterator<D>, java.io.Closeable, java.lang.AutoCloseable, java.util.Iterator<D>
    public class RangeUnionIterator<K extends java.lang.Comparable<K>,​D extends CombinedValue<K>>
extends RangeIterator<K,​D>
    Range Union Iterator is used to return sorted stream of elements from multiple RangeIterator instances. PriorityQueue is used as a sorting mechanism for the ranges, where each computeNext() operation would poll from the queue (and push when done), which returns range that contains the smallest element, because sorting is done on the moving window of range iteration RangeIterator.getCurrent(). Once retrieved the smallest element (return candidate) is attempted to be merged with other ranges, because there could be equal elements in adjacent ranges, such ranges are poll'ed only if their RangeIterator.getCurrent() equals to the return candidate.

    • Method Detail

      • computeNext

        public D computeNext()
        Description copied from class: AbstractIterator
        Returns the next element. Note: the implementation must call AbstractIterator.endOfData() when there are no elements left in the iteration. Failure to do so could result in an infinite loop.

        The initial invocation of AbstractIterator.hasNext() or AbstractIterator.next() calls this method, as does the first invocation of hasNext or next following each successful call to next. Once the implementation either invokes endOfData or throws an exception, computeNext is guaranteed to never be called again.

        If this method throws an exception, it will propagate outward to the hasNext or next invocation that invoked this method. Any further attempts to use the iterator will result in an IllegalStateException.

        The implementation of this method may not invoke the hasNext, next, or AbstractIterator.peek() methods on this instance; if it does, an IllegalStateException will result.

        Specified by:
        computeNext in class AbstractIterator<D extends CombinedValue<K>>
        Returns:
        the next element if there was one. If endOfData was called during execution, the return value will be ignored.

      • close

        public void close()
           throws java.io.IOException
        Throws:
        java.io.IOException